Integrated circuit packages, such as a quad flat package (QFP), small outline integrated circuit (SOC) package and plastic single small outline (PSSO) package include a die pad and an integrated circuit (or die) that is supported on the surface of the die pad. An encapsulating material surrounds the integrated circuit. A plurality of pins, often called leads, such as “gull wing” leads, usually extend from the sides of the encapsulating material forming the package. The leads are connected by bond wires to the encapsulated integrated circuit. Often these types of integrated circuit devices are formed as surface mounted devices. The package form may be a flat rectangular body and often is a square body with leads extending along all four sides. There are numerous design variations, which differ usually in the number of leads, their pitch, the package dimensions, and the materials used to construct the package. Materials often are selected to improve or vary the thermal characteristics of the package.
Quad flat no leads (QFN) packages are similar in design, but have improved coplanarity and heat dissipation and do not have gull-wing leads that act as antennas. As a result, QFN packages create much less “noise” in high-frequency applications as compared to QFP and similar packages. The QFN package includes an integrated circuit die surrounded by an encapsulation material and leads coupled to the IC die and to contact pads exposed on a bottom surface of the encapsulation material adjacent its periphery. QFN packages are known for their small size, cost-effectiveness and good production yields. Because of an exposed lead frame pad (or top die paddle support), these QFN packages provide good thermal performance and remove heat from the package because of the direct thermal path from the exposed lead frame pad.
The contact pads exposed on the bottom surface of the encapsulation material in QFN and similar packages are usually single row pads and the die rests on top of the top die paddle support that cooperates with the lead frame pad. In those cases where the die is small relative to the top die paddle support, delamination may occur because the encapsulation material may separate from one or more of the leads when induced by temperature changes or mechanical stresses. Epoxy bleed-out may also occur when the IC die is initially adhered to the top die paddle support. Also, larger packages may occupy excessive space on the circuit board. It would be advantageous if the QFN package size can be reduced and different IC die sizes accommodated without compromising the die-to-die pad ratio while also reducing delamination and epoxy bleed-out.